Vol. 11  No. 1/2017
© Inštitut za sanitarno inženirstvo, 2017
International Journal of Sanitary Engineering Research4
Indoor environmental 
quality (IEQ) in Slovenian 
children daycare centres.  
Part I: Results of in-situ 
measurements
1 Chair of Buildings and Constructional 
Complexes, Faculty of Civil and Geodetic 
Engineering, University of Ljubljana, 
Ljubljana, Slovenia
2 Infrastructure and Real Estate 
Management Department, European 
Faculty of Law, Nova Gorica, Slovenia
3 Chair of Health Ecology and Control 
Division, Faculty of Health Sciences, 
University of Ljubljana, Ljubljana, Slovenia
*	Corresponding author
 Mateja Dovjak, Chair of Buildings and 
Constructional Complexes, Faculty of Civil 
and Geodetic Engineering, University of 
Ljubljana, Ljubljana, Slovenia 
E-mail: mateja.dovjak@fgg.uni-lj.si
Luka PajEk1, Mitja košIR1, Živa kRIStl2, 
Katarina Kacjan Žgajnar3, Mateja Dovjak1*
abStRact
The number of children enrolled in daycare centres is increasing, while indoor 
environmental quality of Slovenian children daycare centres remains 
insufficiently investigated. The purpose of this paper, as Part I of the larger 
study “Indoor environmental quality (IEQ) in Slovenian children daycare 
centres”, was to holistically assess indoor environmental quality of 24 
playrooms in 17 publicly funded children daycare centres in Slovenia. The 
performed holistic assessment included simultaneous in-situ measurements of 
the selected comfort parameters (i.e. indoor air quality, thermal, visual and 
acoustic comfort), which were compared with legal requirements and 
recommendations. The results of in-situ measurements showed that the most 
critical field was the indoor air quality (in 63% of playrooms cCO2i,avg >1667 
ppm) and that the indoor environmental quality conditions met all of the legal 
requirements and recommendations only in 8% of the investigated playrooms. 
In general, if compared to other EU countries, the conditions in Slovenian 
facilities were slightly worse. Therefore, a holistic approach to the assessment 
of indoor environmental quality is vital to achieve a universally comfortable and 
healthy indoor environment. Part II of this study presents further investigation 
of interrelationship between different building characteristics and IEQ.
key words: indoor environmental quality, in-situ measurements, comfort, public 
buildings, daycare centres
 Original scientific article
Received: 27. 10. 2017 
Accepted: 20. 12. 2017
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 5
 
IntRoDuctIon
The statistical data of EU over the last decade show that the amount of 
enrolled children in children daycare centres (DCCs) has increased [1], 
while in Slovenia almost 77% (84750) of children aged one to five were 
enrolled in DCCs in September 2014 [2]. As the number of children en-
rolled in Early Childhood Education and Care (ECEC) is high and seems 
to be increasing, it is essential that child’s stay in an educational institu-
tion is comfortable and without adverse health effects [3–12], especial-
ly due to the fact that children are more susceptible to environmental 
influences, thus being a vulnerable population with particularly higher 
risk of adverse health effects. 
Therefore, besides executing field measurements of IEQ parameters in the 
selected DCCs, one of the goals of our study was also to get a bigger pic-
ture in the field of IEQ in DCCs. We were particularly interested in existing 
studies in the field of IEQ all across the Europe and wider. In order to ana-
lyse the state-of-the-art in the field of IEQ in educational building facilities, 
a comprehensive literature review was carried out. Table 1 represents 
study summary of 24 selected research papers dealing with indoor envi-
ronment quality in buildings intended for education (e.g. DCCs, schools).
Among the referenced studies (Table 1), the most investigated indoor 
comfort field is IAQ, while the least investigated is visual comfort. Ther-
mal comfort [12–15], indoor air quality (IAQ) [4, 7, 10, 16–23, 30–32], 
visual comfort [5, 6, 8] or acoustic comfort [3, 25–27] and/or their im-
pact on human health is relatively well investigated either in DCCs or in 
schools. In many cases studies identified the conditions as inadequate 
and hazardous for children. Cano et al., Teli et al. [11] and De Giuli et 
al. [29] presented a wider aspect as they investigated two IEQ fields, 
for example, by taking into account thermal comfort and indoor air qual-
ity at the same time. Very few studies of IEQ were made in Slovenian 
DCCs, mostly focusing only on acoustic comfort, for example a study 
made by Kacjan Žgajnar et al. [25]. In addition, the literature review 
showed that there is no such study, which would simultaneously con-
sider all of the four comfort fields (i.e. thermal, visual, acoustic comfort 
and IAQ). 
table 1: An overview of the selected reviewed research papers
comfort 
field
author  
(year)
location Study area Study population Study parameters
thermal 
comfort
Fabbri (2013) 
[13]
Italy, Reggio Emilia,
N = 1 DCC
Thermal comfort 
(PMV, PPD) 
Playrooms with 4–5 
year old children
Tai, RHai, vai, Tmr, PMV, PPD
Hwang et al. 
(2009) [14]
Taiwan,
N = 14 schools
Thermal comfort 
(TSV)
Children 12–17 years 
old
TSV
Mors et al. 
(2011) [15]
Netherlands, 
Eindhoven,
N = 3 schools
Thermal comfort 
(PMV, TSV)
Classrooms with 9–11 
years old children
Tai, RHai, vai, Tmr, PMV, TSV
Yun et al. (2014) 
[12]
S. Korea, Seoul,
N = 10 DCCs
Thermal comfort 
(PMV)
Naturally ventilated 
playrooms with 
children 4–6 years old 
Tai, RHai, vai, Tmr, PMV
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
Children are more susceptible 
to environmental influences, 
thus being a vulnerable 
population with particularly 
higher risk of adverse health 
effects.
© Inštitut za sanitarno inženirstvo, 20176

comfort 
field
author  
(year)
location Study area Study population Study parameters
Indoor air 
quality
Araújo-Martins 
et al. (2014) [16]
Portugal, Lisbon and 
Porto,
N = 45 DCCs
IAQ and health
Playrooms with 3 
months to 6 year old 
children
cCO2i, biological and chemical 
hazards, Tai, RHai
Cars et al. 
(1992) [17]
Sweden, Teleborg 
(Växjö),
N = 7 DCCs
Infectious diseases 
and IAQ
Playrooms in DCCs 
and in renovated 
dwellings
cCO2i, absence due to an 
infectious disease
Daneault et al. 
(1992) [18]
Canada, Montreal,
N = 91 DCCs
IAQ
Randomly selected 
playrooms
cCO2i, Tai, RHai
Gładyszewska-
Fiedoruk (2013) 
[19]
Poland, Białystok,
N = 3 DCCs
Correlation between 
IAQ and RH
Playrooms with 3–6 
year old children
cCO2i, Tai, RHai
Roda et al. 
(2011) [20]
France, Paris,
N = 28 DCCs
IAQ
Playrooms with 
toddlers
cCO2i, biological and chemical 
hazards, Tai, RHai
Ruotsalainen and 
Jaakkola (1993) 
[21]
Finland, Espoo,
N = 30 DCCs
IAQ
Old and new 
playrooms
cCO2i, ventilation rate, 
chemical hazards, odours, Tai, 
RHai,
St-Jean et al. 
(2012) [10]
Canada, Montreal,
N = 21 DCCs
IAQ
Playrooms with a 
capacity of at least 40 
children
cCO2i, chemical hazards, Tai, 
RHai
Stankeviča and 
Lešinskis (2012) 
[22]
Latvia, Riga,
N = 6 DCCs
IAQ
Playrooms in old, new 
and renovated DCCs
cCO2i, Tai, RHai
Zuraimi et al. 
(2008) [23]
Singapore,
N = 104 DCCs
IAQ of DCCs in 
tropical climate
Randomly selected 
playrooms
cCO2i, cCOi, Tai, RHai, vai, 
biological hazards
visual 
comfort
Hathaway et al. 
(1992) [5]
Canada,
schools
Impact of artificial 
and natural light on 
children
Children in classrooms 
with artificial or natural 
daylight
Performance and health 
analysis of children
Heschong 
Mahone Group 
(1999) [6]
USA, California,
N = 3 schools
Impact of daylight 
on children
Children in well and 
under-lit classrooms
Performance analysis of 
children
Nicklas and 
Bailey (1997) [8]
USA, N. Carolina,
N = 5 schools
Impact of daylight 
on children
Children in well and 
under-lit classrooms
Performance analysis of 
children
acoustic 
comfort
Chatzakis et al. 
(2014) [3]
Greece, Crete, 
Heraklion,
N = 10 DCCs
Noise level 18 playrooms Leqi, impact of noise on health
Kacjan Žgajnar 
et al. (2009) 
[24]
Slovenia, Ljubljana,
N = 3 DCCs
Noise level in the 
workplace 
Educators in playrooms 
intended for children 
between 3 and 6 years 
old
Leqi, impact of noise on health 
of educators
Kacjan Žgajnar 
et al. (2009) 
[25]
Slovenia, Ljubljana,
N = 3 DCCs
Noise level in 
playrooms
Playrooms intended for 
children between 3 
and 6 years old
Leqi, impact of noise on health
McAllister et al. 
(2009) [26]
Sweden, Linköping,
N = 3 DCCs
Noise level in 
playrooms
10 children without 
reported hearing 
problems
Leqi, impact of noise on health
Sjödin et al. 
(2012) [27]
Sweden, Umea°,
N = 17 DCCs
Noise level in the 
workplace
Educators impact of noise on health
Multiple 
comfort 
analysis
Cano et al. 
(2012) [28]
Portugal, Lisbon,
N = 19 DCCs 
IAQ and thermal 
comfort
125 playrooms 
intended for children 
old between 3 months 
and 6 years
Tai, RHai, vai, Tmr, cCO2i, cCOi, 
biological and chemical 
hazards
De Giuli et al. 
(2014) [29]
Italy, Padua,
N = 3 schools
IAQ, thermal 
comfort and visual 
comfort
8 classrooms in 
primary schools
Tai, RHai, vai, To, PMv, PPD, 
cCO2i, Ei
Teli et al. (2012) 
[11]
England, Hampshire,
N = 1 school
IAQ and thermal 
comfort
Classrooms with 
children between 7 
and 11 years old
Tai, RHai, vai, Tmr, PMV, PPD, 
TSV, cCO2i
Tai – indoor air temperature; RHai – indoor air relative humidity; vai – indoor air velocity; Tmr – mean radiant temperature; To – operative temperature; 
PMV – predicted mean vote index; PPD – predicted percentage of dissatisfied; TSV – thermal sensation vote; cCO2i – indoor concentration of 
carbon dioxide; cCOi – indoor concentration of carbon oxide; Leqi – indoor equivalent noise level; Ei – daylight illuminance of work plane
L. Pajek, M. Košir, Ž. Kristl et al. Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 7
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Therefore, it can be concluded that these four areas of comfort in DCCs 
are not treated equally, as some are represented in the research less of-
ten than others. In this respect, in recent years the importance of high 
quality ECEC is reflected in a high volume of joint reflection on policies 
and programmes between the European Commission and the Member 
States [33]. As can be seen, the IEQ of children daycare centres as well 
as other educational institutions was relatively well investigated through-
out the facilities across the EU and wider, which was found out through 
the review of the published papers. Surprisingly, the quality of indoor en-
vironment in Slovenian DCCs has not been sufficiently investigated. Con-
sequently, the objective of our study was to examine the situation in Slov-
enian DCCs from the IEQ perspective. Therefore, measurements of 
selected parameters of visual, thermal and acoustic comfort, as well as 
indoor air quality were carried out. Several playrooms were sampled from 
the selected DCCs in Slovenia in order to execute in-situ measurements 
of the selected comfort parameters. Hence, the above mentioned factors 
affecting human comfort in buildings were investigated in 24 playrooms 
in 17 DCCs. The study took place from March to June 2013. The indoor 
environment was investigated in order to improve IEQ conditions in DCCs. 
The latter was done by examining minimal criteria according to national 
and EU legal requirements, applicable recommendations or standards. 
MEthoDS
area and time of observation
The research was carried out in 17 randomly selected children daycare 
centres (anonymised and denominated by letters A–R) located in Slove-
nia, which included 24 playrooms intended for children aged 3 to 5. 
The research took place at targeted DCCs from March to June 2013. 
The conducted research protocol is presented in Figure 1.
Figure 1: 
Research protocol
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
© Inštitut za sanitarno inženirstvo, 20178

Measurements
The required data were collected in-situ in the selected DCCs by re-
searchers conducting measurements of the studied parameters. Meas-
urements took place in forenoon, particularly between 9 and 12 am 
(i.e. after breakfast and before lunch) in occupied playrooms. Holistic 
evaluation of IEQ included the following measurements. Indoor air tem-
perature (Tai), indoor air relative humidity (RHai), indoor air velocity (vai) 
and surface temperature (Tsurf) were measured to evaluate thermal com-
fort of the investigated playrooms. Field technicians measured daylight 
illuminance of work plane (Ei) and window glass light transmittance (LT) 
as the selected visual comfort parameters. To evaluate the IAQ, indoor 
concentration of carbon dioxide (cCO2i) was measured. Indoor equiva-
lent noise level (Leqi) was the selected and measured parameter of 
acoustic comfort. In addition, two selected outdoor parameters were 
measured: outdoor noise level (Leqe) and outdoor concentration of car-
bon dioxide (cCO2e). For the purpose of the study the following meas-
urement equipment was used: Testo 445 (Tai, RHai, vai), Testo 535 
(cCO2i, cCO2e), Raytek Raynger MX (Tsurf) and Voltcraft DT 8820 (Leqi, 
Leqe, Ei). Outdoor air temperature (Tae), relative humidity of outdoor air 
(RHae) and air velocity (vae) were provided by Slovenian Environment 
Agency [34].
All the selected indoor parameters were recorded every 20 minutes, 
with the exception of carbon dioxide concentration, which was recorded 
every 5 minutes. Measuring instruments were placed out of children’s 
reach. A typical selection and position of measuring points is presented 
on a floor plan of playroom A1 (Figure 2). 
Figure 2: 
Measurement points in playroom A1
L. Pajek, M. Košir, Ž. Kristl et al. Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 9
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All of the measurements were taken at a height of 0.70 m above the 
floor, with the exception of surface temperature measurements, which 
were taken on all the circumferential surfaces. Although the work plane 
for horizontal illuminance measurements in DCCs should be positioned 
lower than at 0.70 m above the floor, this distance was nevertheless 
used in order to prevent inquisitive children interfering with the measure-
ments. However, presuming that the illuminance at lower work planes is 
higher than at 0.70 m, the measurements are on the safe side. Measure-
ments of daylight illuminance were performed for the actual state of play-
rooms – positions of furniture and shading systems were preserved. All 
the sources of artificial light were turned off. Indoor environment condi-
tions were evaluated and compared to legal requirements and recom-
mendations for DCCs, defined in the following documents:
• Slovenian national legislation: O.J. RS, No. 42/02, 105/02 [35]; 
O.J. RS, No. 73/00, 75/05, 33/08, 126/08, 47/10, 47/13 [36]; 
O.J.RS, No.17/06, 18/06 – ed., 43/11 – ZVZD-1[37];
• Slovenian national guidelines: TSG-1-005:2012 [38];
• International standards and recommendations: ANSI/ASHRAE 
Standard 62.1-2007 [39]; CEN CR 1752:2001[40]; EN 12464-
1:2011[41]; EN 15251:2010[42]; ISO 7730:2005 [43].
Preparation of data
All the required data were collected and prepared for further investiga-
tion. The dimensions (i.e. floor space, height, window openings) and 
orientation of the DCC playrooms were recorded by the field techni-
cians. DCC managers provided information regarding lists of children 
present in the analysed playrooms and the age of buildings. For the pur-
pose of evaluating indoor environmental quality, additional calculations 
of playroom floor area per occupant, playroom volume, mean radiant 
temperature (Tmr), predicted mean vote index (PMV), predicted percent-
age of dissatisfied (PPD), window to floor ratio (WFR), illuminance uni-
formity (i.e. Ei,min/ Ei,avg and Ei,avg/ Ei,max) and percentage of dissatisfied 
with the air quality (PPDIAQ) were made. Thermal comfort parameters 
were calculated according to ISO 7730:2005. The calculation of PPDIAQ 
parameters was performed with the use of Equation 1 based on CEN 
CR 1752:2001.
PPDIAQ = 395
(–15.15(cCO2i,avg – cCO2e)
–0.25) (1)
RESultS
Sample building characteristics 
For the purpose of further analysis, in initial step sample building charac-
teristics were investigated, as one of the potential factors that could affect 
IEQ. All of the investigated DCCs were publicly funded; none of them was 
privately run. In 2013 the average age of the selected buildings was 43 
years, with the average year of construction 1970. The oldest building in 
the entire sample was constructed in 1899, as a residential villa; the 
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
© Inštitut za sanitarno inženirstvo, 201710
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newest was constructed in 2013 as a low-energy children daycare cen-
tre. Eight out of seventeen buildings were recently renovated with the aim 
to lower their energy demand. All of the DCCs were renovated only by re-
placing windows. Playrooms in every DCC were naturally ventilated, with 
the exception of DCCs P and R, which were ventilated mechanically. The 
latter DCCs were also classified as low-energy buildings and were at the 
same time the youngest buildings (Table 2) included in the study. The 
average floor area of the selected playrooms was 41.3 m2 and the aver-
age volume 132.2 m3. The average floor area per occupant was 2.2 m2. 
Only minority of playrooms (17%) had the average floor space equal to or 
higher than what is required by the Slovenian legislation (i.e., at least 3 
m2/child) [36]. None of the investigated playrooms had north orientation, 
with most of them (i.e. 9) oriented south. Basic information and building 
characteristics of each selected DCC facility are presented in Table 2.
table 2: Basic information and building characteristics of the selected DCCs
Daycare 
centre
Year of 
construction
Recent 
renovationb
Playroom 
no.
Playroom 
occupation 
(children + 
staff) 
Floor 
area 
[m2]
Floor area 
per occupant 
[m2/occ]
volume [m3]
area of 
windows 
[m2]
orientation of 
majority of 
windows, 
azimuth [°]
A 1952 Yes
A1 14 + 2 35.7 2.2 102.2 7.3 W, 290
A2 20 + 2 35.8 1.6 112.2 10.3 W, 290
B 1979 Yes B1 19 + 2 52.7 2.5 155.5 16.8 W, 292
C 1899 Yes C1 14 + 2 35.2 2.2 131.5 11.5 E, 100
D 1963 No
D1 18 + 2 44.6 2.2 161.1 20.8 NW, 310
D2 16 + 3 37.2 2.0 116.8 15.5 S, 178
D3 16 + 1 46.9 2.8 142.6 13.8 SE, 130
E 1906 No E1 14 + 2 36.3 2.3 127.4 3.3 W, 275
F 1979 No F1 19 + 3 39.0 1.8 116.5 14.8 E, 100
G 1979 Yes
G1 14 + 2 41.9 2.6 151.7 10.0 S, 160
G2 14 + 2 36.0 2.3 164.2 13.1 SE, 150
H 1976 Yes H1 16 + 2 44.6 2.5 133.8 16.7 SW, 210
I 1973 Yes I1 18 + 2 43.7 2.2 128.6 15.0 SE, 142
J 1982 No
J1 20 + 2 33.8 1.5 113.3 11.5 SE, 128
J2 15 + 2 32.9 1.9 111.0 11.8 S, 149
K 1976 Yes
K1 18 + 2 38.2 1.9 99.4 10.7 E, 80
K2 21 + 2 46.8 2.0 145.9 13.4 SE, 128
L 1976 No L1 20 + 2 41.0 1.9 132.8 18.4 S, 172
M 1979 No M1 14 + 3 42.4 2.5 122.1 9.9 SW, 220
N 1971 No N1 17 + 2 50.3 2.6 174.5 21.5 S, 180
O 1972 Yes
O1 13 + 2 44.7 3.0 134.1 11.6 S, 200
O2 17 + 2 49.1 2.6 146.3 13.2 S, 158
Pa 2013 No P1 21 + 2 39.2 1.7 118.0 17.3 S, 178
Ra 2012 No R1 17 + 2 43.6 2.3 132.2 15.4 S, 164
a Low-energy DCCs; b Energy retrofit: replacement of windows
Measurement and calculation of the selected IEQ parameters
The highest measured outdoor air temperature during the measurement 
time interval (9–12 am) was 32.4 °C, and the lowest –1.4 °C [34]. In 
the same way, the average value of measured outdoor CO2 concentra-
tion was 387 ppm (330–445 ppm), the average outdoor equivalent 
noise level 50 dB (30–75 dB). Table 3 represents general characteristic 
values of measurements and calculations of the selected IEQ parame-
ters in all the playrooms among the analysed DCCs. The measured val-
L. Pajek, M. Košir, Ž. Kristl et al. Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 11
 
ues of thermal and visual comfort parameters were largely dispersed. 
Thus, in Table 3 the median values were used instead of arithmetic 
mean, to represent general conditions in playrooms. The main results of 
IEQ measurements compared with legal requirements and recommen-
dations are presented in the subsections below.
table 3: Measured and calculated values of indoor environmental quality parameters among all the 17 DCCs (24 playrooms)
Parameters
Symbol Description unit Min Max Median
Tai indoor air temperature °C 19.3 27.4 23.7
tsurf surface temperature °C 13.5 34.2 22.3
Rhai indoor air relative humidity % 29.1 68.5 47.2
vai indoor air velocity m/s 0.00 0.50 0.04
PMv predicted mean vote - –0.33 1.10 0.19
PPD predicted percentage of dissatisfied % 5 29 6
lt light transmittance of windows - 0.52 0.89 0.69
WFR window to floor ratio % 9.1 45.0 30.0
Ei average indoor daylight illuminance lx 44 2655 352
- uniformity of illuminationa - 0.01 0.38 0.17
cco2i indoor CO2 concentration ppm 389 3613 1400
PPDIaQ predicted percentage of dissatisfied with IAQ % 9 43 27
leqi indoor equivalent noise level dB 30 95 70
a Ratio between minimal and average illuminance.
Thermal comfort 
During the conducted measurements indoor air temperature did not 
meet the required values (i.e., 19–24 °C) according to Slovenian legal 
requirements [35] in 37% of playrooms. In those playrooms the air 
temperature was too high, with the highest values reached in playroom 
R1 (25.5–27.4 °C). However, in relation to the recommendations [42]) 
(i.e., 17.5–22.5 °C), the recommended indoor air temperature was en-
sured only in 8% of the playrooms, with too high air temperatures in 
the majority of the playrooms. Radiant temperature asymmetry was not 
detected in any of the analysed playrooms. Nevertheless, the lowest 
surface temperature of 13.5 °C was measured on the external wall sur-
face in playroom G1, as a consequence of present thermal bridge. In-
door air relative humidity was within the acceptable limits of 40 to 60% 
[36, 42] in 54% of the playrooms, while in other playrooms the air was 
mostly too dry (i.e. RHai < 40%). The measured indoor air velocity ex-
ceeded the permitted value (i.e., vai < 0.19 m/s) [35] in 17% of the 
playrooms and the recommended value (i.e., < 0.15 m/s) in 29% of 
the playrooms. However, according to the recommendations [35, 42], 
appropriate PMV and PPD (i.e.,± 0.7 PMV, PPD < 15%) values were 
still achieved in 83% of the playrooms.
Indoor air quality (IAQ)
In 63% of the playrooms the measured concentrations of CO2 exceeded 
the value permitted by Slovenian legislation (i.e., < 1667 ppm) [35]. 
Overall, nearly 80% of the playrooms had mean CO2 concentrations ex-
ceeding 1000 ppm, which is recommended as the highest value in the 
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
During the conducted 
measurements indoor air 
temperature did not meet the 
required values according to 
Slovenian legal requirements 
in 37% of playrooms.
In 63% of the playrooms the 
measured concentrations of 
CO2 exceeded the value 
permitted by Slovenian 
legislation.
© Inštitut za sanitarno inženirstvo, 201712

ANSI/ASHRAE Standard 62.1-2007 [39]. The highest achieved mean 
CO2 concentration measured in playroom B1 was 2584 ppm, while the 
highest measured value of 3613 ppm was reported in playroom R1. 
According to standard EN 15251:2010 [42] and Equation 1, 8% of the 
investigated playrooms were classified as indoor air quality class I (PP-
DIAQ < 15%), 17% of playrooms were classified as class II (PPDIAQ < 
20%), 33% as class III (PPDIAQ < 30%) and the rest as class IV (PPDI-
AQ > 30%). In more than half of the playrooms, the PPDIAQ value was 
higher than 25%.
Visual comfort
One playroom (E1) did not meet the requirement of Slovenian legislation 
for the WFR in DCCs (i.e., > 20% of the floor plan) [36, 42]. Playroom 
L1 had the highest percentage of lighting openings in relation to the 
floor area (45%) due to its supplementary clerestory windows. The 
maximum ratio between the height and the depth of the playrooms is 
limited by Slovenian legislation to 2.5 [36, 42]. In contradiction to the 
legal requirements, in 18% of playrooms the room depth was more 
than 2.5 times greater than the room height. According to standard 
[42], in 54% of the playrooms the recommended average work plane 
illuminance of at least 300 lx was ensured by daylighting during the 
time of conducted measurements.
Acoustic comfort
In general, high noise levels in the selected playrooms were a conse-
quence of children activity in the playrooms. In most cases the internal-
ly generated noise was dominant over the external ambient noise sourc-
es. According to Slovenian legislation [38], indoor noise level was in 
general too high during the measurements. Only 58% of the playrooms 
met the Slovenian legal requirements for noise exposure at work (i.e., < 
70 dB) [37]. However, it has to be noted that noise level measurements 
were performed only for the period of three hours, while the legal re-
quirements consider the noise exposure during the entire time span of 
operating hours. The highest and the lowest mean indoor noise levels 
were 83 dB (playroom A2) and 51 dB (playroom F1). Although indoor 
equivalent noise level was adequate in the majority (67%) of playrooms, 
it has to be noted that also the impulse noise should be taken into con-
sideration. Maximum noise levels in some playrooms exceeded 90 dB 
due to high children activity (e.g. playing, singing).
holistic assessment 
In order to holistically assess the IEQ in the analysed DCCs, all of the 
four aspects of comfort must be simultaneously evaluated. For each as-
pect one parameter was selected for a holistic assessment. Thus, PMV 
was selected to evaluate thermal comfort; average work plane illumi-
nance with daylight was selected to evaluate visual comfort, indoor CO2 
concentration for IAQ and equivalent noise level for acoustic comfort. 
Table 4 represents the selected parameters of observation and general 
measurement results in all the 24 investigated playrooms.
L. Pajek, M. Košir, Ž. Kristl et al. Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
Maximum noise levels in 
some playrooms exceeded 
90 dB due to high children 
activity (e.g. playing, singing).
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 13
 
table 4: Measurement results of the selected basic parameters in each playroom
thermal 
comfort
visual comfort IaQ
acoustic 
comfort
Playroom no. PMv [-] Ei,avg [lx] cco2i,avg [ppm] leq,i,avg [db]
A1 0.01 139 1643 64
A2 –0.05 449 1805 83
B1 –0.30 492 2584 71
C1 0.09 136 1400 70
D1 0.33 697 1389 67
D2 0.25 918 2094 80
D3 0.69 356 1176 61
E1 0.09 74 1000 67
F1 0.43 1285 1449 51
G1 0.03 126 1433 65
G2 0.29 183 1657 60
H1 –0.33 347 1812 74
I1 0.13 690 2020 75
J1 0.66 682 1910 69
J2 0.31 162 761 65
K1 0.72 294 905 75
K2 0.31 97 628 71
L1 0.12 521 1012 64
M1 –0.02 121 1967 74
N1 –0.02 463 867 69
O1 0.42 44 1125 70
O2 0.13 163 1192 75
P1 0.75 915 1181 76
R1 1.10 2655 2023 67
Furthermore, the measured values were compared to the recommended 
ones. Such comparison is presented in Figure 3. The measured values 
of thermal and visual comfort parameters were largely dispersed. Thus, 
in Figure 3 the median values were used for all of the comfort types. 
Figure 3: 
Comparison of the selected IEQ fields 
and their parameters for playrooms 
A1–R1, considering parameters of 
thermal, visual, acoustic comfort and 
indoor air quality. Solid line represents 
the recommended value and dotted 
line represents the median value of 
the playrooms. The PMV values are 
shown as absolute numbers.
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
© Inštitut za sanitarno inženirstvo, 201714

If the results are holistically observed, in playrooms A1 and A2 (8% of 
playrooms) all of the IEQ fields were within the recommended values. In 
10 playrooms (42%), only one IEQ field did not meet the recommended 
values. In the rest of playrooms (50%), two or three uncomfortable IEQ 
parameters were identified simultaneously. None of the investigated play-
rooms had all the selected IEQ parameters inappropriate.
DIScuSSIon
Poor thermal conditions of indoor environment can have negative im-
pact on comfort and learning skills or may even cause adverse health 
effects, since children are more sensitive to high air temperatures than 
adults [12]. The measured air temperatures in the playrooms, which 
were considered within this paper, were similar to those in the studies 
conducted in Canada [18], Portugal [16] and Latvia [22], but higher 
than those in Portugal [44] and lower than those measured in South 
Korean [12] or Singaporean [23] facilities.
Inadequate control over air humidity of living environment can result in 
suitable conditions for the growth of mould, which has adverse effects 
on occupants’ health [45–47]. The RH values, which were measured in 
DCCs during the presented study, were found to be less appropriate 
(i.e. lower) than those measured in Canada [18], Portugal [28], Italy 
[13], France [20] or South Korea [12]. At the same time, they were 
more suitable than in Singapore DCCs [23]. However, the latter is cli-
mate consequence of Singapore’s high humidity climate. 
The measured mean air velocity in the selected DDCs was similar to the 
values identified by Mors et al. [15] in Netherlands and Yun et al. [12] 
in South Korea. On the other hand, they were lower than those meas-
ured in Singapore by Zuraimi and Tham [23]. In contrast to previously 
conducted studies [16, 22, 28], where occupants were satisfied with 
thermal comfort or the reasons for discomfort were too cold thermal 
conditions, the PPD values identified by measurements of this study 
were more affected by too warm indoor environment.
The identified CO2 concentrations (an indicator of ventilation rates) in the 
investigated Slovenian DCCs were similar to those measured in Portugal 
[16], Canada [10, 18], Latvia [22] and Poland [19], where in most cases 
the measured CO2 concentrations exceeded 1000 or 2000 ppm. How-
ever, in comparison to studies conducted in Scandinavian countries [17, 
21, 31], France [20] and in Singapore [23], where the average CO2 con-
centrations rarely exceeded 1000 ppm, the measured CO2 concentra-
tions in Slovenian DCCs were higher and, thus, less appropriate.
The results of the conducted measurements of horizontal daylight illumi-
nance (Figure 3) show that in 37% of the analysed playrooms the aver-
age illuminance values were below the recommended value of 300 lx de-
fined in EN 12464. However, it has to be emphasized that only 
daylighting was investigated (i.e. measured), although the recommenda-
tions of the EN 12464 standard relate to lighting in general (i.e. daylight-
ing and artificial lighting). Among the studied playrooms in Slovenian 
DCCs, the most common reasons for poor daylighting were the window 
L. Pajek, M. Košir, Ž. Kristl et al. Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
The results of the conducted 
measurements of horizontal 
daylight illuminance show that 
in 37% of the analysed 
playrooms the average 
illuminance values were below 
the recommended value of 
300 lx defined in EN 12464. 
International Journal of Sanitary Engineering Research Vol. 11  No. 1/2017 15
 
properties (i.e. area, shape, type of glazing, etc.). In addition, the penetra-
tion of daylight was often obstructed by various items attached to the 
glazing (e.g. shaped paper, drawings). One of the reasons for visual dis-
comfort was also the inappropriate use of shading devices. In other 
words, in some playrooms shades were in shading position when shading 
was not needed (e.g. overcast sky, shading of western windows in fore-
noon). In several playrooms the shading system was even damaged and 
therefore inoperable for the users. This is a common problem in public 
buildings, as identified also by De Giuli et al. [29] in their study. 
Excessive noise levels in DCCs represent health risk and discomfort for 
children and staff, which has been considered by numerous studies 
[25–27]. The measured noise levels in the investigated playrooms were 
comparable to the findings of some other studies [25, 26] and were 
relatively high. The problem of excessive noise levels in Slovenian DCCs 
might be additionally amplified by inappropriate reverberation times, 
which were highlighted by the findings of Kacjan Žgajnar et al. [48].
concluSIonS
Holistic approach to the assessment of indoor environmental quality with 
all the IEQ fields taken into consideration is vital to achieve a universally 
comfortable and healthy indoor environment. All the parameters of IEQ 
are by some means directly or indirectly interconnected. Thus, they can-
not be assessed separately one at a time. Although some authors (see 
references [29, 49]) do not advise ranking of buildings with a combined 
assessment index, a holistic approach is still necessary, where as many 
comfort parameters as possible should be investigated simultaneously, 
but not necessarily combined into a single rating. Therefore, a multi-disci-
pline approach and cooperation of experts from different professional 
fields is encouraged. There are very few studies that would comprehen-
sively and simultaneously investigate thermal comfort, indoor air quality, 
visual and acoustic comfort. Within the presented paper such approach 
was used to assess playrooms in the selected DCCs. The IEQ conditions 
in some of the investigated playrooms did not meet the recommended 
criteria. However, it must be noted that there was no playroom where all 
of the four considered comfort types would be inadequate. Moreover, it 
has to be stressed that the measurement results showed that in 42% of 
the investigated playrooms only one comfort field deviated from the mini-
mal required and the recommended values (Figure 3). The one uncom-
fortable condition could stay unidentified if not all the comfort fields were 
analysed. Contrasting other studies, which deal predominantly with IEQ, 
the presented results show the importance of holistic approach.
An in-depth analysis of the collected data showed that among the 24 
studied playrooms the most critical field of indoor environmental quality 
was IAQ with 75% of playrooms above the recommended value (1000 
ppm). The percentage of playrooms that exceeded the recommendations 
in the fields of visual and acoustic comfort was also relatively high, with 
46% and 38%, respectively. Comparatively, thermal comfort recommen-
dations were exceeded only in 8% of considered playrooms, thus defining 
 L. Pajek, M. Košir, Ž. Kristl et al.Indoor environmental quality (IEQ) in Slovenian children daycare centres. Part I: Results of in-situ...
The problem of excessive 
noise levels in Slovenian 
DCCs might be additionally 
amplified by inappropriate 
reverberation times, which 
were highlighted by the 
findings of Kacjan Žgajnar et 
al. [48].
Contrasting other studies, 
which deal predominantly 
with IEQ, the presented 
results show the importance 
of holistic approach.
© Inštitut za sanitarno inženirstvo, 201716

thermal comfort as the most controlled. According to previously conduct-
ed studies (see references [11, 12, 15]), the IEQ recommendations and 
legal requirements for buildings intended for children should be reconsid-
ered, since children response to the indoor environment differently than 
adults. In addition, the results of this paper indicate that the legislation 
regarding IEQ in Slovenian DCCs might be insufficient, since the identi-
fied IEQ was better in some other EU countries with generally stricter le-
gal requirements for indoor environment, e.g. Denmark, France and Swe-
den [50]. This study or similar ones (see reference [30]) can be used to 
provide a useful evidence base for the formulation and targeting of poli-
cies for improving IEQ in school or daycare buildings. Part II of this study 
further examines the interrelationship between various building character-
istics, occupants’ behaviour and several parameters of IEQ.
acknowledgements
This study was conducted in collaboration with the selected children 
daycare centres in Slovenia. The children daycare centres included in 
the research were randomly selected and were given free choice to par-
ticipate or not in the research. The authors gratefully acknowledge the 
cooperation of the managers and educators of the participating day care 
centres, field technicians and other project collaborators.
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